Research on spacecraft and powerplant integration problems Spacecraft analysis topical report

Nuclear-electric power generating requirements for unmanned scientific solar system probe

Parametric study of prospective early commercial MHD power plants (PSPEC). General Electric Company, task 1: Parametric analysis

The performance and cost of moderate technology coal-fired open cycle MHD/steam power plant designs which can be expected to require a shorter development time and have a lower development cost than previously considered mature OCMHD/steam plants were determined. Three base cases were considered: an indirectly-fired high temperature air heater (HTAH) subsystem delivering air at 2700 F, fired by a state of the art atmospheric pressure gasifier, and the HTAH subsystem was deleted and oxygen enrichment was used to obtain requisite MHD combustion temperature. Coal pile to bus bar efficiencies in ease case 1 ranged from 41.4% to 42.9%, and cost of electricity (COE) was highest of the three base cases. For base case 2 the efficiency range was 42.0% to 45.6%, and COE was lowest. For base case 3 the efficiency range was 42.9% to 44.4%, and COE was intermediate. The best parametric cases in bases cases 2 and 3 are recommended for conceptual design. Eventual choice between these approaches is dependent on further evaluation of the tradeoffs among HTAH development risk, O2 plant integration, and further refinements of comparative costs

The Synchronous Rotor Instability Phenomenon—Morton Effect

TutorialThis paper gives an overview on the “Morton Effect” and explains how synchronous rotor instability, due to non-uniform heating of bearing journals, can occur in high-speed turbomachinery. The paper was also presented in 2008 as a tutorial paper. Now, 10 years later, the paper has been updated with the latest published information on this subject. The phenomenon is clearly explained and an overview is given of the existing literature on this subject

Design of a 50-watt air supplied turbogenerator

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008.Includes bibliographical references (p. 77-79).This thesis presents the design of a high-pressure-ratio, low-flow turbogenerator with 50 W electrical power output, designed to operate from a 5-bar air supply. The research shows that a MEMS-based silicon turbine in combination with a micro-machined generator can meet the design objectives of the turbogenerator. The turbogenerator architecture comprises a single-stage radial inflow turbine and a direct coupled cylindrical permanent-magnet synchronous generator. To address its key design trade-offs and fundamental engineering challenges, the design space is first explored in terms of the key design variables: device diameter and rotor shaft speed. To guide the selection of the two variables, a simplified model for the scaling of turbine and generator power is developed. Next, the integrated turbine and generator design is analyzed and designed in detail. The minimum manufacturable turbine blade span is identified as the key challenge imposed by the low flow requirement. Furthermore, the small scale of the blades results in high rotational speeds. Since the turbine and generator are integrated, the high speed makes the generator design challenging because of manufacturing tolerances, material stress limitations and losses. Thus, the design trade-off is between generator complexity and turbine blade manufacturability. The analysis shows that the viable low-flow 50 W turbogenerator design space is narrowly constrained by the minimum blade span and the 5-bar pressure supply, demanding MEMS fabrication for the short turbine blades. A single-stage MEMS radial turbine is designed in detail, and assessed for performance and manufacturability. The rotor speed at design conditions is 450,000 rpm with a rotor radius of 5 mm, a rotor blade span of 200 um, and a blade tip clearance of 20 um.(cont.) Based on 3D RANS simulations, the turbine is predicted to achieve 48% total-to-static adiabatic efficiency and to produce 77 W of shaft power at a turbine mass flow of 1.45 g/s. Assuming a generator efficiency of 80% and a power electronics efficiency of 90% yields a net electrical turbogenerator power output of 50 W. End-wall losses are dominant in the planar turbine and a diffuser is included to reduce the pressure losses in the right exit turn. The final high-speed, low flow design integrates a MEMS turbine and a meso-scale permanent-magnet synchronous generator combined with hybrid ball bearings.by Stevan Jovanovic.S.M

Detection of Rotor Cracks

Special PaperPg. 129-140The method of detection of rotor cracks by vibration monitoring is outlined. Various mechanisms stimulating cracks are discussed. Vibration measuring instrumentation and diagnostic methodology for early detection of rotor cracks are described

Space Laser Power Transmission System Studies

Power transmission by laser technique is addressed. Space to Earth and space to space configurations are considered

SU2: The Open-Source Software for Non-ideal Compressible Flows

The capabilities of the open-source SU2 software suite for the numerical simulation of viscous flows over unstructured grid are extended to non-ideal compressible-fluid dynamics (NICFD). A built-in thermodynamic library is incorporated to account for the non-ideal thermodynamic characteristics of fluid flows evolving in the close proximity of the liquid-vapour saturation curve and critical point. The numerical methods, namely the Approximate Riemann Solvers (ARS), viscous fluxes and boundary conditions are generalised to non-ideal fluid properties. Quantities of interest for turbomachinery cascades, as loss coefficients and flow angles, can be automatically determined and used for design optimization. A variety of test cases are carried out to assess the performance of the solver. At first, numerical methods are verified against analytical solution of reference NICFD test cases, including steady shock reflection and unsteady shock tube. Then, non-ideal gas effects in planar nozzles and past turbine cascades, typically encountered in Organic Rankine Cycle applications, are investigated and debated. The obtained results demonstrate that SU2 is highly suited for the analysis and the automatic design of internal flow devices operating in the non-ideal compressible-fluid regime

Overview of NASA Electrified Aircraft Propulsion Research for Large Subsonic Transports

NASA is investing in Electrified Aircraft Propulsion (EAP) research as part of the portfolio to improve the fuel efficiency, emissions, and noise levels in commercial transport aircraft. Turboelectric, partially turboelectric, and hybrid electric propulsion systems are the primary EAP configurations being evaluated for regional jet and larger aircraft. The goal is to show that one or more viable EAP concepts exist for narrow body aircraft and mature tall-pole technologies related to those concepts. A summary of the aircraft system studies, technology development, and facility development is provided. The leading concept for mid-term (2035) introduction of EAP for a single aisle aircraft is a tube and wing, partially turbo electric configuration (STARC-ABL), however other viable configurations exist. Investments are being made to raise the TRL level of light weight, high efficiency motors, generators, and electrical power distribution systems as well as to define the optimal turbine and boundary layer ingestion systems for a mid-term tube and wing configuration. An electric aircraft power system test facility (NEAT) is under construction at NASA Glenn and an electric aircraft control system test facility (HEIST) is under construction at NASA Armstrong. The correct building blocks are in place to have a viable, large plane EAP configuration tested by 2025 leading to entry into service in 2035 if the community chooses to pursue that goal

A fully-integrated multi-watt permanent-magnet turbine generator

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 331-336).The energy density available from batteries is increasingly becoming a limiting factor in the capabilities of portable electronics. As a result, there is a growing need for compact, high energy density sources. This thesis presents the design, fabrication, and testing of a fully-integrated permanent-magnet turbine generator based on silicon MEMS technology envisioned to replace batteries. The air-driven device, supported on gas bearings, has been experimentally shown to deliver 19 mW to matched resistive loads of 0.33 [omega] while operating at a rotational speed of 40 krpm. With an active volume of 41 mm³, this translates to a power density of 0.46 mW/mm³. By extrapolating the experimental data up to the design speed of 360 krpm, it is expected that the integrated generator can deliver 1.5 W of output power.This research represents the first batch-fabricated permanent-magnet generator shown to generate milliwatt-level power, with a further potential to deliver watt-level power. To achieve full integration, a broad range of topics are examined, including the design of gas bearings, high-speed mechanical analysis using non-ideal material interfaces, magnetic rotor balancing, and novel fabrication techniques.A major challenge unique to the integrated device is the need for both silicon and non-silicon components on the same die. While the silicon components are precision micromachined using DRIE and can withstand high temperatures, the permanent magnets are laser-machined separately and rapidly demagnetize when exposed to heat. Similar problems exist for the copper surface windings. The differences are reconciled with the use of a novel drop-in technique, which involves placing nonsilicon components into the die after all the silicon fabrication is complete.by Bernard Chih-Hsun Yen.Ph.D

The Synchronous Rotor Instability Phenomenon—Morton Effect

TutorialThis paper gives an overview on the “Morton Effect” and explains how synchronous rotor instability, due to non-uniform heating of bearing journals, can occur in high-speed turbomachinery. The paper was also presented in 2008 as a tutorial paper. Now, 10 years later, the paper has been updated with the latest published information on this subject. The phenomenon is clearly explained and an overview is given of the existing literature on this subject